I'm sure they were all planned as doubles. Unfortunately things often end up working out differently in practice, particularly with the lack of RDW at the moment.All TPE Hope Valley services appear to be only 3 cars today. Given Doncaster to Scunthorpe is blocked for engineering work there should be more units available. It also appears at least 3 units are stabled at Cleethorpes (plus 2 operating Scunthorpe to Cleethorpes). It really shouldn't be too difficult to have planned more units available in traffic.
When there's a Doncaster to Scunthorpe block on, stabling limitations mean that it's not really practicable to use any of the 6 units usually stabled at Cleethorpes on the west side of the block. Though as I say, that shouldn't prevent all services from being booked doubles. But it may impact on things if there are issues on the day.